Forge Build Part I – Building the Forge Burners

Part I: Building the Forge Burners

A forge is just an insulated shell without a burner (or multiple forge burners in my case). So the first thing I did was set out on building the forge burners. I built them with parts from the plumbing aisle of my local big box hardware store.

A rule of thumb when building a forge is to have one of these 3/4″ propane burners for every 350 cubic inches of forge volume. The shell I am using (an old compressed air tank I got on Craigslist for $20) will allow me to have about 650 cubic inches of volume when I consider the 2″ of insulation around the inside.

Both completed burners ready for a home.

Clean burning flame at about 10 PSI.

Burner Tube Preparation

To begin, I took my section of 12″ long 3/4″ pipe and drilled holes every 90º around the tube that was about 3″ long. First with a small drill bit for pilot holes, and then followed by a larger bit. I then finished up with a file to turn the many holes into long slots.

Gas Accelerator Assembly

With the main body slotted, I moved to the ‘gas accelerator assembly’. This is just a 1/8″ NPT brass nipple with a MIG welder tip. To get the brass tube through the black iron 3/4″ end cap, I put it in my lathe and used that to drill a hole in the center of the cap that is barely big enough for the brass nipple to slide through. I then drilled and tapped a hole on the side of the cap for a set screw to ensure it stays put. I put a 1/8″ brass end cap on the lathe and drilled out the center and tapped it to accept the MIG tip.

Gas accelerator assembly.

Using lathe to drill straight hole for the gas accelerator assembly to slide through and mount.

Burner Choke Sleeves

Now for the choke sleeves. These control the air flow by adjusting the air-fuel mixture. I used 1″ iron pipe which nicely telescopes with the 3/4″ pipe. I cut a section about a half inch longer than the slots and cleaned it up. I chucked it on my lathe to sand a smooth slope towards the inside on one end which helps with air flow. Then I added a set screw and moved on to the nozzles.

Choke tube after being cleaned up on the lathe.

Burner Nozzles

We have an example of when I was too excited and forgot to take good pictures. The nozzles are made of 1.5″ pipe about 2.5″ long with a 3/4″ long 1″ pipe that acts as a collar to close the gap between the 3/4″ pipe and the 1.5″ pipe. It was a snug fit that I welded together, which you can see in the second image. I, of course, had to test them out before moving on to building the main body.

Size comparison between handheld MAPP gas torch and the new propane forge burner.